Pneumatic yarn splicing devices of the basic type identified above are disposed as a rule in stationary fashion at the work stations of automatic bobbin winding machines, as is known from numerous publications such as German Patent Disclosures DE 36 37 033 A1 or DE 40 05 752 A1. The design and function of such yarn splicing devices is also described at length in the manual entitled "Autoconer 238" by the Schlafhorst Corporation.
In such devices, an automatic yarn joining and/or cop changing mechanism is activated via the computer of the affected winding station in the event of a yarn break and when it is necessary to change the feed cop or bobbin which delivers the yarn being wound. More specifically, a suction nozzle is first placed against the surface of the takeup bobbin being wound, which is rotating slowly counter to the winding direction. Once the upper yarn end trailing from the takeup bobbin has been engaged, the suction nozzle pivots back to its original starting position, in which the suction nozzle opening is positioned below the splicer. In the process, the length of yarn extending between the takeup bobbin and the suction nozzle is drawn into an electronic cleaner located above the yarn splicing device, a clamping and cutting device positioned in that region, and, under the guidance of corresponding guide contours of yarn guide baffles and yarn guide hoops, into the scissors blades of a cutting device located below the splicer. During this placement process, the upper yarn also slides over the back of a yarn catching hook positioned above the splicer and enters the region of an opened upper yarn clamp.
Virtually simultaneously with the suction nozzle, a gripper tube positioned in a lower starting position pivots into an upper working position and in so doing carries a lower yarn end drawn off the feed cop or bobbin by means of a yarn tensioner with which the yarn end has been held. When the gripper tube pivots into its upper working position, the lower yarn, likewise guided on corresponding yarn guide contours similarly to the upper yarn end, slides into an opened lower yarn clamp, an opened upper cutting device, and a fork-like recess in the yarn catching hook.
The yarn catching hook swivels inwardly to lay the upper and lower yarns into the bottom of the splicing chamber of the pneumatic splicer. The upper yarn is also drawn into the upper yarn clamp in the process. The yarn end fixed in the upper and lower yarn clamps are cut to the correct length in the associated cutting devices and prepared for the ensuing splicing by opening the respective yarn ends in yarn opening tubes. The prepared yarn ends are fed in parallel relation to one another into the splicing chamber, typically in the form of an elongate channel, by special yarn drawing-in devices, and the yarn ends are swirled together pneumatically to accomplish spliced intermingling and twisting of the constituent fibers of the yarn ends.
While the winding station starts up again, the yarn catching hook pivots in a defined fashion back to its original position and in the process slowly releases the spliced yarn.
The above-described devices have proven themselves in practice to produce very good yarn splices. However, these devices have the disadvantage of a relatively expensive and complicated construction.